The present invention relates to a method and apparatus for determining the properties of fiber pulp by taking a fiber pulp batch of a predetermined volume, by measuring its temperature and by filtering water from it by means of a pressure difference.
From publications Svensk Papperstidning, 9 (1977) 265-284 and Pulp & Paper 55 (1981) 72-75 there are known various methods and devices for determining the properties of fiber pulp. In these methods the consistency of the fiber suspension is first measured and, when necessary, the fiber suspension is diluted to a consistency suitable for the measuring. In the first-mentioned publication it is noted that the suitable consistency is approximately 1 g/liter for unrefined fibers and approximately 0.25 g/liter for refined fibers and groundwood pulp. In the second publication the fiber suspension must be diluted to a consistency of approximately 0.5%. The method according to the first-mentioned publication is based on measuring the pressure difference produced across the fiber layer filtered onto the wire while the flow of liquid through the wire is constant, and the method according to the second-mentioned publication is based on measuring the flow velocity of liquid through the fiber bed while it is subjected to constant pressure. In addition, in both methods the temperature of the fiber suspension is measured, and other properties of the fiber pulp can be calculated on the basis of the measurements obtained.
By the above-mentioned methods it is not possible to determine the consistency of the fiber suspension, and this has to be analyzed separately before the beginning of the determination. In addition, these prior known determination methods can be applied only to very dilute fiber suspensions, and thus they seldom can be applied directly to specimens taken from the process flow, but the specimen must first be diluted to the suitable consistency. Also, these prior known measuring methods do not provide reliable results when the properties of pulps having a high shive content, for example pulps from under the pulpstone of a pulp grinder, are being determined. Furthermore, these methods of determination are relatively sensitive to air present in the fiber suspension; in general, the air must first be removed from the fiber suspension before the determination is started.
The object of the present invention is to provide a method and device for determining the properties of fiber pulp, a method by which the properties of a fiber pulp, including its consistency, can be determined, for example, directly from the process flow, without prior dilution, by which it is also possible to determine the properties of pulps having a high shive content, such as pulps from under the pulpstone in a pulp grinder, and in which air possibly present in the fiber suspension does not in any way hamper the measuring.